New detections of C18O(1-0) emission in massive young stellar objects

Observations of the C18O(1-0) line emission toward 74 massive young stellar objects or candidates were carried out using the 13.7m millimetre wave telescope of Purple Mountain Observatory at Qinghai Station. 63 of the observed objects show the emission and 57 of these are new detections. Based on the observed radiation temperature (TR∗) and line width at half intensity (ΔV), the optical thickness of C18O(1 - 0) and column density of C18O are derived for each such source under LTE. The intensity ratio and integrated intensity ratio between the 13CO(1-0) and C18O(1 - 0) lines are also discussed.